Subsystem optical interconnections using long-wavelength LD and singlemode-fiber arrays

Subsystem optical interconnections for lengths of over 100 m are proposed. Single-mode fiber (SMF) arrays and very-low-threshold-current long-wavelength laser diode (LD) arrays realize small-skew and error-free interconnections. The LD turn-on delay and receiver risetime and falltime (t_r/t_f) skews are considered in addition to the electronic and fiber skews, and a total skew of less than 1.65 ns is obtained. It is shown that an SMF array with a skew of 2.1 ps/m is needed to obtain a small skew. The LD array can be coupled with an SMF array to give high signal-to-noise ratio and error-free transmission. Driving each LD at a modulation current of six times the threshold current results in an LD turn-on delay skew of less than 500 ps. Wideband preamplifiers with low feedback resistivity reduce receiver t_r/t_f skew. The total skew of 1.65 ns gives a transmission speed of less than 150 MB/s (150 Mb/s/ch×8 ch) through a 100-m fiber array